The present invention is directed to photo-active cyclopentadienylplatinum (IV) compounds, and to irradiation-curable silicone compositions containing such compounds as photo-active platinum (IV) catalysts.
Drahnak, U.S. Pat. No. 4,600,484, is directed to a hydrosilylation process involving the addition between silicon hydride compounds (i.e. compounds containing the Si-H moiety) and compounds containing aliphatic unsaturation. Drahnak discloses that his process is activated by actinic radiation. Drahnak uses a platinum complex having the formula, EQU CpPt(R).sub.3, (1)
where Cp is cyclopentadienyl and R is a C.sub.1-18 aliphatic organic radical.
The Drahnak catalyst consists of a cyclopentadienyl group, Cp, eta-bonded to a platinum (IV) group, Pt(CH.sub.3).sub.3, which is substituted with three sigma bonded aliphatic radicals. It is also reported in U.S. Pat. No. 4,600,484, that the cyclopentadienyl group Cp can be further modified with organosilyl groups.
Boardman et al., U.S. Pat. No. 4,916,169, shows a visible light-activated hydrosilylation process for effecting the addition of a silicon hydride to compounds containing aliphatic unsaturation. In accordance with the hydrosilylation practice of Boardman et al., a polycyclic aromatic organic compound, such as anthracene, is physically blended as a sensitizer with a photo-active platinum compound, such as shown by formula (1). Based on the theory of Boardman et al., the sensitizer effects a visible light energy transfer to further enhance the photo-activation of the platinum compound. While beneficial cure results are reported by Boardman et al., it has been found that the sensitizer is sometimes incompatible in the silicone curable silicone mixture and/or a large amount of sensitizer is required to be effective.
It would be desirable therefore to provide additional procedures for improving the efficiency of photo-activated platinum (IV) compounds as catalysts for effecting the cure of irradiation-curable silicone compositions.
Further, it would be desirable to provide photo-active platinum compounds comprising a cyclopentadienyl group chemically combined to a Pt (IV) group, which did not require the separate blending of an incompatible organic material, such as anthracene, into an irradiation-curable silicone mixture.